Helmand provincial Governor Assadullah Wafa says foreign planes bombed a village in the Sangin district late on Tuesday. He says 21 civilians, including women and children, were killed.

But a man from the bombed village of Sarwan Qala says about 30 died.

The US-led coalition, which is separate to the 37-nation NATO-led force, has only said it was involved in an "engagement" in the same area of Sangin.

It has confirmed it called in "air support" amid intense battles with Taliban fighters in the southern province of Helmand that killed an unknown number of rebels and a coalition soldier.

Coalition spokesman Major Chris Belcher says the coalition is not aware that civilians have been killed.

"There were enemy casualties in [the] operation last night - I don't have an exact number," he said.

The coalition says it and Afghan soldiers battled Taliban fighters in Helmand for around 16 hours on Tuesday.

It is smarting from claims of mounting civilian casualties after nearly 60 other people were said to have been killed in its operations late last month, according to investigations and residents.

Afghan President Hamid Karzai summoned commanders of the coalition and the separate NATO-led force, and other top foreign diplomats, last week to protest.

The Helmand Governor says he has sent a team to the area to establish what had happened.

Meanwhile, the Pentagon has announced plans to keep about 25,000 troops in Afghanistan through next year amid a resurgence of the Taliban.

The Pentagon says the 101st Airborne Division will send its headquarters and a combat brigade to Afghanistan early next year to replace units returning to the US.

Despite strains on US forces because of the war in Iraq, Defence Secretary Robert Gates decided in January to beef up the US military presence in Afghanistan from one combat brigade to two to help counter a revival of the Taliban.

There are about 25,000 US troops in Afghanistan, about 14,000 of them assigned to the 36,000-strong NATO-led International Security Assistance Force.